The origin of the Neoplatonist doctrine of the henads has been imputed to Iamblichus, mostly on indirect evidence found in later Neoplatonists, chiefly Proclus. Is there any trace of this concept to be found in the extant works or fragments of Iamblichus himself? The best candidates among his surviving texts are the excerpts in Psellus of his volume on Theological Arithmetic from his Pythagorean series, and the first book of de Mysteriis , where Iamblichus answers Porphyry's questions on the nature of the gods. Such evidence as can be found there would most likely deal with the divine henads, given the subject matter of the text. Certain repeated items of vocabulary appear as technical usages that form the basis for arguing that Iamblichus already has in mind if not the explicit concept henad at least its functional equivalent: the term monoeides occurring in both the Psellan excerpts and de Mysteriis, and in the latter, mostly in Book I, the stated attributes of a high, divine principle uniting the gods which are also designated by Proclus as typical of the divine henads, particularly in the propositions of the Elements of Theology defining the henads. Iamblichus in Book I also ascribes to the gods the same role in the process of ellampsis as Proclus does for the divine henads. A theory is also advanced concerning the possible development of the concept of the henad by Iamblichus, based in part on the polemical nature of de Mysteriis and his relationship to Porphyry